This invention relates to a metal-rolling roll assembly and more particularly to a bearing assembly for supporting a cylindrical metal-rolling roll during a rolling operation.
Conventional rolling mills fall into three categories: two-high, four-high and miscellaneous mills. The two-high mills, include two rolling (or work) rolls supported by roll neck bearings. Two-high mills generally use rolls of relatively large diameters in order to achieve high roll stiffness. Large diameter rolls also permit larger roll-neck bearings thereby increasing the maximum rolling force available. Roll stiffness is an important factor in the quality of the finished product; generally, the stiffer the roll (its resistance to bending deflections), the flatter the finished strip. For several reasons, however, small roll diameters are desirable for rolling rolls. With small roll diameters, the size and cost of the overall mill assembly is reduced. Also, a roll of small size requires a lower rolling force for a given work piece thickness reduction, and also allows thinner products to be rolled. Additionally, small roll size leads to a reduction in roll-face contact pressures, total rolling friction, and the required driving torque for turning the roll.
The conflict between the desirability of large roll diameter for stiffness and high rolling force and the aforementioned advantages of smaller roll size has been resolved traditionally by replacing two-high mills with four-high mills or miscellaneous mills (three-high, five-high, six-high, cluster mills, planetary mills, etc.) The four-high mills utilize small diameter rolling (work) rolls supported throughout their lengths by larger diameter backup rolls. The backup rolls thus provide the desired stiffness for resisting radial deflections of the work rolls. The large diameter backup rolls also permit the use of large roll neck bearings for high maximum separating (i.e. rolling) force. Although four-high and miscellaneous mills do meet the technical objectives for accomplishing large thickness reductions in a single mill stand and for producing good quality finished products, there are disadvantages to this approach. The major disadvantages of the four-high and miscellaneous mills over two-high mills are the greater mechanical complexity, larger size, and higher cost, both initial and operating, as compared with the simpler two-high mills. Additionally, the surface of the product from four-high and miscellaneous mills is of poorer quality under some operating conditions than that produced in two-high mills.
The rolls in two-high, four-high and miscellaneous mills are supported at their ends by roll neck bearings of three general types: tapered roller, oil film, and sleeve. These bearings usually require a continuous, flowing supply of lubricating oil. Often this bearing lubricant is incompatible with the metal rolling lubricant and coolant, necessitating two well-isolated recirculating systems. These require elaborate oil seals and complex fitting and assembly procedures which add both to operating and initial costs. The fact that roll necks often require accurate tapers, steps, and grooves for the seals and bearings also adds to costs. Roll neck bearings are disadvantageous, too, in that only the roll ends are supported during a rolling operation. Thus, lateral deflections of the roll while rolling metal are not significantly prevented when rolls with these bearings are utilized.
An object of the present invention, therefore, is to provide a new design for a rolling mill assembly which permits simple and low cost rolling mills capable of accomplishing large thickness reductions while making high quality products.
Another object of this invention is to provide a new bearing design which makes possible the use of small diameter rolling rolls (without backup rolls) in the production of high-quality finished products without the need for separate bearing and metal rolling lubricants and the attendant seals to keep the two lubricants apart.
A still further object of the invention is to provide a bearing design for accomodating small diameter rolls which minimizes the amount of lateral roll deflections produced when the roll is used in a rolling operation.
Yet a further object of the invention is to provide a bearing design which makes roll maintenance and roll changing easy.
Other objects, features, and advantages of the present invention will become apparent from what follows.